PROJECT SUMMARY/ABSTRACT There is no cure for cystic fibrosis (CF), which is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) genes. Life expectancy is only 42 years, with 85% of the mortality due to complications from lung disease. Owing to the buildup of mucus in the lungs, which is a hallmark of CF, patients suffer chronic bacterial infections of a variety of Gram-positive and Gram-negative species, most notably Pseudomonas aeruginosa and Staphylococcus aureus. These are complicated further by the formation of bacterial biofilms within CF sputum and by the emergence of multi-drug resistant organism (MDRO) strains (QED1). Very high antibiotic dosages are needed for eradication of biofilm infections, which can lead to serious adverse side effects. The current standard of care for CF patients with P. aeruginosa infections is treatment with the aminoglycoside, tobramycin, administered via inhalation with a nebulizer or dry powder inhaler. Some CF centers employ colistin, which is a cationic antimicrobial peptide (CAP), as a second line of antibiotic therapy; however, there is not an approved inhalation form of colistin in the U.S., and systemic administration is not recommended due to the risk of nephrotoxicity. There is no approved drug delivery technology that addresses the simultaneous need for lung-specific delivery and the challenge of penetrating a lung environment rich with mucus and colonized with chronic bacterial biofilms. Our laboratory has developed graft polyelectrolytes with ?smart,? surface-active chemistry that facilitates self-assembly with charged biomolecular cargoes and passage across physiological barriers that limit drug distribution. We hypothesize that these surface-active polyelectrolytes can be tuned to self-assemble with both CAPs and aminoglycosides to form nanoparticles that can subsequently be aerosolized using a nebulizer. Furthermore, we hypothesize that these aerosolized nanoparticles will provide improved penetration into the mucus hydrogel-like environment of the lungs of CF patients, enable controlled release, and exert improved activity against biofilms of P. aeruginosa and other strains common to CF patients. In order to test these hypotheses and provide proof of concept for this approach, which is readily translatable and potentially a game-changer for CF patients, we will: (1) develop polyelectrolyte nanoparticles loaded with tobramycin and colistin (individually and in combination) and investigate their controlled release behavior; evaluate the ability of the surface-active nanoparticle to penetrate mucus and biofilm barriers and their antimicrobial activity; and (3) evaluate the regional and systemic exposure of mice to carrier and drug payload following administration either systemically or by nebulizer inhalation.